One conventional type of infusion pump system employs a peristaltic pump in conjunction with an intravenous administration set. The set consists of flexible thermoplastic tubing through which fluid flows from a suspended container, such as a flexible bag or rigid bottle, to a patient's indwelling vein access device, such as a needle or cannula inserted into the patient. A length of the administration set tubing between the fluid container and the patient is mounted in the peristaltic pump which sequentially squeezes adjacent sections of the tubing so as to pump the fluid via a peristaltic action along the tubing into the patient.
To insure that such pumping systems function satisfactorily, such pumping systems typically include a system for sensing air bubbles in the liquid flowing in the tubing in the pump. If the control system senses a sufficient amount of air, then an alarm is actuated and/or the operation of the pump is terminated. The air sensor control system for the pump may permit a small bubble to be pumped through the tubing without actuating the alarm or shutting the pump down, but the control system will actuate an alarm and/or shut down the pump if the rate of small bubble flow exceeds a preselected value. The pump control system will also generate an alarm and/or shut down the pump if the length of a single bubble has a size which exceeds a predetermined length along the tubing.
A conventional air sensor employed in such peristaltic pumps is a piezoelectric transmitter/sensor assembly which has a slot for receiving a length of the tubing. The tubing, which is typically a flexible polyvinyl chloride material, is squeezed lightly between the opposed walls of the slot. In the piezoelectric transmitter/sensor assembly, there is a piezoelectric transmitter transducer in one of the walls, and there is a piezoelectric receiving transducer in the other wall.
The piezoelectric transmitter transducer is electrically powered to produce mechanical vibrations. The mechanical vibration is transmitted as ultrasonic energy through the wall of the tubing into the liquid. At the receiving side of the slot, the energy passes from the liquid through the wall of the tubing and into the receiving transducer. The ultrasonic energy is attenuated, scattered, or reflected dependent upon the conditions within the fluid. At the wall opposite the transmitter transducer, the receiver transducer converts the energy into an electrical signal which varies as a function of the energy transmission through the liquid. This signal can be correlated as function of the presence or absence of an air bubble.
If the wall of the tubing is not in good contact with the sides of the slot in the sensor assembly, then the transmission of the ultrasonic energy from the transmitter transducer into and through the wall of the tubing will be degraded. Similarly, there will be a degradation of the ultrasonic energy at the other side of the slot as the energy passes from the tubing wall to the receiving transducer. The signal is greatly attenuated owing to the poor contact between the tubing and the walls of the sensor slot, and this results in the generation of a smaller electrical signal. A sufficiently small signal could be of the same, small magnitude that would occur if there was an air bubble in the fluid. Thus, the control system would provide a false alarm and/or shut down the pump. In view of this, it would be desirable to provide a system in such a pump for facilitating the proper loading of the tubing within the air sensor slot so as to minimize the possibility of false alarms arising from poor contact between the tubing and slot walls.
One type of conventional pump has a door which is pivotally mounted to the pump housing for movement between (1) a closed position covering the tubing in the pump, and (2) an open position which permits loading or unloading of the tubing. Initially, the tubing can be manually loaded in the pump with a length of the tubing pushed at least part way into the air sensor slot. The inside of the pump door has a projecting finger. When the door is closed, the projecting finger engages the tubing and pushes it further into the air sensor slot to ensure good contact between the wall of the tubing and both of the opposed walls of the air sensor slot.
While the above-described, door-mounted pusher finger may function generally satisfactorily, it would be desirable to provide an improved system for ensuring proper positioning of the tubing within the air sensor slot. In particular, it would be especially advantageous to provide a tubing-engaging system which could be mounted on a door and which could accommodate an offset location of the door pivot axis with respect to the air sensor slot. Such an improved system should accommodate engagement of the tubing in the air sensor slot by the door in such a way that the tubing is contacted, and moved further inwardly into the slot, along a path of movement that does not urge the tubing against the slot walls with unequal force or in a manner that would tend to push part of the tubing away from one of the walls and toward the other wall.
The present invention provides an improved pump system which can accommodate designs that have the above-discussed benefits and features, which is convenient to use, and which is cost-effective with respect to its manufacture and operation. The system is especially suitable for use in a peristaltic pump. However, the system is applicable to other types of pumps that have a tubing-receiving slot which can be covered with a door.
The system is easily operated and can be used with a wide variety of standard administration sets and fluid containers. The system is designed to meet the growing demand for hospital-wide standardization, as well as alternate-site, in-home healthcare standardization.